The invention relates to polymeric materials that are used to conduct electrical signals, and relates in particular to conductive adhesives that are used with medical monitoring sensors that are placed directly on a patient, such as an electro-cardiogram (EKG) sensor.
Electrically conductive pressure-sensitive adhesives for use in biomedical applications are disclosed, for example, in U.S. Pat. No. 4,848,353. Since such conductive materials typically depend on the presence of water, however, the material must be maintained in a sealed environment until being used. See also, U.S. Pat. No. 5,143,071, which discloses non-stringy adhesive gels for that are hydrophilic.
Such substances must be isolated from the environment prior to use (e.g., in sealed packages), and may function improperly if allowed to lose water from the conductive material. These limitations adversely affect both the cost of sensors that use such conductive adhesives as well as the amount of use that any particular sensor may enjoy.
There is a need therefore, for a material that may be used to conduct electricity yet is not susceptible to variations in the water vapor content of the environment in which it is used.